Joze senegacnik rt_topics
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Joze senegacnik rt_topics Joze senegacnik rt_topics Presentation Transcript

  • Measurement Errors
  • I/O Bottleneck Problem Response Time Component Time % Elap AvgEla ---------------------------------------- ----------- ------- --------- CPU service 3934.97s 48.39% 0.000716 un-accounted for time 1363.01s 16.76% db file sequential read 1122.00s 13.80% 0.032253 gc buffer busy 451.73s 5.56% 0.011746 log buffer space 451.64s 5.55% 0.123974 buffer busy waits 176.79s 2.17% 0.029579 gc cr block 2-way 156.49s 1.92% 0.003287 gc cr grant 2-way 100.20s 1.23% 0.006541 latch: cache buffers chains 98.92s 1.22% 0.005708 gc current grant 2-way 69.68s 0.86% 0.006728 latch: library cache 30.10s 0.37% 0.010030 row cache lock 28.95s 0.36% 0.018727 gc current block 2-way 26.72s 0.33% 0.003828 gc cr block busy 19.35s 0.24% 0.006802 gc current grant busy 15.30s 0.19% 0.004999 latch: row cache objects 14.28s 0.18% 0.006165 gc cr block 3-way 11.73s 0.14% 0.002952 gc current block 3-way 11.34s 0.14% 0.003440 log file sync 10.71s 0.13% 0.315066 enq: SQ - contention 9.14s 0.11% 0.060911
  • Timings for Single Block Reads – 3 node RAC Single Block Read Times From AWR 0 5 10 15 20 25 30 35 40 45 50 0:00 1:40 3:20 5:00 6:40 8:20 10:00 11:40 13:20 15:00 16:40 18:20 20:00 21:40 23:20 Snapshot ID - 20 minutes interval SingleBlockReadTimein Milliseconds Inst 1
  • Timings for Single Block Reads – 3 node RAC Single Block Read Times From AWR 0 5 10 15 20 25 30 35 40 45 50 0:00 1:40 3:20 5:00 6:40 8:20 10:00 11:40 13:20 15:00 16:40 18:20 20:00 21:40 23:20 Snapshot ID - 20 minutes interval SingleBlockReadTimein Milliseconds Inst 1 Inst 2 Inst3
  • The Facts About The I/O Bottleneck Problem • Facts: – 3 node RAC – Same storage – Single block read time for Instance 1 was substantially different from read times for other instances during off hours – 5 batch jobs during off hours • The timings for Instance 1 are obviously not correct • The sandwich syndrome (output from strace) gettimeofday({1159440978, 931945}, NULL) = 0 pread(14, "6242003752302+254.000160054001050"..., 8192, 455 057408) = 8192 gettimeofday({1159440978, 944159}, NULL) = 0 • Waiting in runque for CPU exaggerates all wait times of the process.
  • Database Connection Problems
  • Too many sessions • 35000 sessions per instance • database level 70000 (2-node RAC)
  • http://www.youtube.com/watch?v=xNDnVOCdvQ0